Muffler with eccentric passage through baffle bodies



United States Patent 11113,545,566

[72] Inventor ThoreJohannes Abrahamsson [56] References Cited Frolunda Swede" UNITED STATES PATENTS APPLNQ 7824,35 1,020,163 3/1912 Swain 181/69 122 Filed 1166.9, 1968 l.087,398 2/1914 Persson 181/49 [45] Patented Dec.8, 1970 A In ted 1,769,778 7/1930 new H l8l/69X 8 2,395,005 2/1946 ,Kuhn 181/58ux [32] P m 3,092,206 6/1963 Moreau 181/68 [33] o y FOREIGN PATENTS 31 No,17,1 4 7 466,712 5/1937 GreatBritain 181/50 432,147 9/1967 Switzerland 181/56 [54] MUFFLER WITH ECCENTRIC PASSAGE THROUGH BAFFLE BODIES 9 Claims, 18 Drawing Figs.

[52] U.S. Cl 181/50, l8l/6l, l8l/63, l8l/69 [51] lnt.Cl F0ln1/10, FOln 7/18 [50] Field ofSearch l8l/49, 50,

Primary ExaminerRobert S. Ward, Jr. Attorney-Holman, Glascock, Downing and Seebold ABSTRACT: An elongated muffler body comprising an outer shell and an internal passage is subdivided perpendicularly to its longitudinal axis into a number of bodies. The passage part in at least some of the bodies is located eccentrically with respect to the longitudinal axis, and an adjustment of the damping and/or throttling capacity of the muffler is brought about by an angular displacement of the bodies.

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PATENTED DEC 8 I976 SHEET 3 BF 3 FIG. 27

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Infvlovfng J: flfiknunmssox 7 M v M BACKGROUND OF THE INVENTION The present invention refers to an absorption muffler of the type comprising an axial perforated passage surrounded by a cover enclosing a sound absorbing material.

It has earlier been proposed for instance in ventilation plants, to dampen the annoying sound by means of mufflers of this type, and also by means of a type having astraightpassage in which a number of baffles parallel to the flow of air are arranged. These baflles are located in a common housing and consist. each of a perforated cover completely filled with mineral wool, or the like. A disadvantage of both types is that they are not adjustable with respect to thedampening capacity and to the resistance to flow.

, The dimensions of the passages, the quantity of air, and also the intensity of the sound will vary considerably within different parts of the same ventilation plant, and'of course also from plant to plant. It is of considerable importance to be able to adjust the muffler according to the need at the specific occasion. An adjustment of the muffler in a ventilation plant may be brought about by a change of the pressure drop across the muffler, which for instance may be obtained by throttling means. The throttling, however, will also itself generate a sound, which means that-a considerable throttling, will require an efficient muffler. In order to be able to fit the above-mentioned types of mufflers to varying demands'it is necessary to store a number of different sizes, both as to length and crosssectional area. a

SUMMARY OF THE INVENTION The present invention has taken .the above-mentioned problems into consideration and is founded on the fact, that the efficiencyof a muffler is proportional to the internal surfaces thereof. The invention is suitable on such occasions, where a dampening of the sound is desired only, or where a dampening as well as a pressure reduction is desired. The invention is essentially characterized by that the muffler perpendicularly to. the passage therethrough is subdivided into number of bodies, that the part of the passage pertaining to at least some of the bodies is eccentrically located in relation to the longitudinal axis of the muffler, and by that the bodies are designed to be angularly displaced in relationto each other in t such a manner that the parts of the passagelocated in the different bodies maybe brought to different relative positions.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 schematically shows a longitudinalsection through a muffler according to the invention with a straight passage and without any throttling.

FIG. 2 is a section along line II-II in FIG. 1.

FIG. 3 shows the mufiler according to FIG. 1 with a maximum throttling and adjacent bodies in an 180 turned position.

FIG. 4 is an end view of the muffler of FIG; 3.

FIG. 5 shows the throttling with adjacent bodies in an 90 I turned position.

FIG. 6 is an end view of the muffler of FIG. 5,.

FIG. 7 shows a further embodiment corresponding to FIGS. 1, 3 and 5, but with a modified mutual position of the bodies.

FIG. 8 is an end view of the muffler of FlGzx7.

. FIG. 9 shows on a larger scale an end view of a body having an eccentric passage. I I

FIG. 10 is a section along line X-X in FIG. 9.

FIG. 11 is an-end view of a body corresponding to that of FIG. 9, but designed as gable portion of a muffler.

FIG. 12 is a section along line XII-XII in FIG, 11.

FIGS, 13 and 15 each show an end view ofan intermediate body, and gable body, respectively, having a concentric passage.

FIG. 14 and 16 are section along XIV-XIV and I XVI-XVI, respectively, in FIGS. 13 and :15.

FIG. 17 shows a perspective view of an assembled muffler according to the invention, and

FIG. 18 schematically shows a longitudinal section through a mufiler having a concentric connection piece- DESCRIPTION OF THE PREFERRED EMBODIMENTS The muffler according to the invention comprises a number of uniform, separate bodies 1, which each forms a self-com tained unit, and which are adapted to be fitted together in appropriate numbers.

As shown in FIGS. 9-16 each body consists of an outer cylindrical shell 2 to which is fitted two end surface plates 3, into which a tubular, perforated passage part 4 is fitted. This is according to FIGS. 9-12 located eccentrically in relation to the longitudinal axis of the body. In the enclosure formed by the components, outer shell 4, end surface plates 3 and passage part 2, a sound absorbing material 5, for instance mineral wool, is stuffed. Each plate 3 of the body is provided with a perforated portion 7, which is located around the passage 4, and the extent of which is defined by a circular sur-- face, which is concentric with the longitudinal axis of the body. Instead of having perforated plates a wire mesh may of course be used to form the end surfaces of the bodies. The bodies which fonn the gable portions of the muffler, and which hereafter will be referred to as gable bodies differ from the intermediate bodies thereby, that one end surface thereof is provided with a connection piece 6, which is an elongation of the part of the passage 4 within the gable portion. Said end surface will furthermore lack any perforations: The bodies are preferably made into types la and lb. Th first type la is of the above described type, and is thus provided with an eccentric passage. The second type lb is provided with a concentric passage, the radius of which is that much bigger than the radius of the eccentric passage as corresponds to the eccentricity of said passage in relation to the longitudinal axis of the body. The bodies of the second type, 1b, i.e. bodies having a centric passage may, in the same manner as above described, be utilized as gable bodies, and thus be provided with a connection piece 6.

FIGS. l8 illustrate four examplesof different mutual location of the bodies. In FIGS. 1 and 2 the'eccentric passage parts are located in such a manner, that a straight flow passage is obtained. The muffler will on this occasionserve'as simple absorption muffler withoutany throttling. On this occasion only the perforated envelop surface of the passage with serve as dampening surface.

In FIGS. 3 and 4 each element has been turned 180 in relation to the adjacent one, whereby the pressure drop across the muffler will be considerably increased, partly due to the air being compelled to follow a sinusoidal pathand partly due to the restrictions which are formed.

FIGS. 5 and 6 shows how the pressure drop across the muffler may be adjusted by turning the bodies 1a in relation to each other. The air will on this occasion be compelled to follow a helical path. In this embodiment the bodies have a square cross section, in such a manner that the volume of the absorbing material may be increased. The angular displacement of the bodies in relation to each other may with this type of body only be 90, or a multiple thereof, if the exterior of the muffler shall have a prismatic shape.

FIGS. 7 and 8 show both types on bodies combined to a muffler, in which two bodies each having an eccentric'passage are followed by a body having a concentric passage and increased passage area, in such a manner that the fluid passing through the mufiler will alternatingly be subjected to expansion'and throttling. This effect may be brought about several times, and of course the angular position of the different types of bodies, and the position of the passage in relation to the longitudinal axis is arbitrary.

If the bodies have a cylindrical cross section it is possible, by a turning of individual bodies having an eccentric passage, to obtain a smooth throttling of the pressure. A throttling will always bring about a sound, but as the perforated areas 7 of the end surface plates 3 are uncovered when the bodies are brought into throttling position the sound absorbing surface is increased. A muffler according to the invention will thus automatically compensate for sounds issuing as a result of a throttling.

The bodies according to FIGS. 9-16, which each consists of a closed plate shell are adapted to be fitted together to a unit comprising two gable bodies and number of intermediate bodies. These are locked together by means of a shroud 8 or the like (FIG. 17). The shroud 8 consists of a tubular member which is slit open in its longitudinal direction. A number of clasps 17 force the edges of the slit portion together, thereby locating the bodies in any desired position/By releasing the clasps it is easy toreadjust the mutual position of the bodies. To facilitate such an adjustment the bodies may preferably be provided with a pin and slot mechanism, in which an elongated curved slot 9 and a pin 10 determine the mutual position between two bodies. In order to bring about different combinations between two adjacent bodies two slots 9 and 9b having different length are arranged at each end plate 3, the corresponding locating possibilities being also providedfor the pins. By turning such a body the longer slot 9b or the shorter slot 9a may be brought to cooperate with the pin 10, and thus a larger or a smaller angle be pennitted. As shown in FIG. 9 the pin 10 may be formed as a screw, whichalternatively may be mounted in any of two threaded bores 11 in the end plate of the body. I

As shown in FIG. 17 the shroud 8 is provided with a transverse slot 12, opposite the middle body of the series. The middle body is in its outer shell provided with-a number of holes 13, into which an adjusting lever 14 may be inserted, and by means of which the series of interconnected bodies may be turned with a certain angular delay in relation to each other, in such a manner that the desired adjustment is obtained.

The embodiment according to FIGS. 1 and 2 differ from'the above described therein that each body' comprises an inner perforated tubular passage part 40, and an outer tubular shell part 2a between which member of insulating material interconnecting the tubular parts is fitted. The-member may be molded from synthetic resin to suitable shape and having comparativelylarge poves. The different muffler bodies are maintained in position by means of separate gable plates 18, each provided with a connection piece 60 having the same eccentric position as the passage part 4a in the bodies. The gable plates 18 are interconnected by means of stay bolts 15, which by means of nuts 16 or the like may be brought to lock the bodies together. Packing plates (not shown) may possibly be located between the individual bodies. The latter are on this occasion not enclosed by a shroud and in order to facilitate an adjustment of the mutual position of the passage parts, marks are made on the outer shell part of the bodies in such a manner that it is easy to find out the mutual position between two passage parts in adjacent bodies.

The bodies are made of different sizes and the connection pieces 6 are made to fit the different sizes of conduits in the ventilation plant. The difference in size between a connection piece to an element of type In, having an eccentric passage, and a connection piece to an element of type 1b, with concentric passage, is preferably chosen to correspond to a step in a scale in such a manner that a body will suit also to the conduit having one size smaller or one size larger dimension, respectively. In this manner it is possible todesign the muffler as a long narrow unit, or as a short but thicker unit, as might be called for with respect to available space.

The embodiments shown and described are to be regarded as explanatory rather than limiting with respect to the invention. The outer shell or the bodies may have an arbitrary cross section, for instance square, rectangular or the like. The fitting together of the elements may be brought about in many different ways, and the bodies may be permanently fitted together for instance by bonding, weldingor the like, once they have been brought to the proper, adjusted position.

I claim: 1. In an absorption muffler:

a number of basically uniform bodies each composed of an outer tubular shell part and an inner perforated tubular passage part as well as a layer of insulating material therebetween, the passage part in at least some of the bodies in the muffler being eccentric in relation to the longitudinal axis of the body; and

means to lock the bodies together in any desired angular position to form a passage extending through the muffler structure.

2. A muffler according to claim 1 in which the bodies are of two main types, in one of which the passage part is eccentric in relation to longitudinal axis, and a second one, in which the passage part is located centrically, the radius of said last mentioned passage part being that much larger that the radius of the first mentioned eccentric passage part as corresponds to the eccentricity of said part in relation to the longitudinal axis.

3. A muffler according to claim 1 in which the bodies forming the gables of the muffler are each provided with a connection piece forming an axial elongation of the passage part in the pertaining body.

4. A muffler according to claim 1 inwhich the tubular shell portion and the tubular passage part of each body are interconnected by end plates to form a drumlike structure enclosing the insulating material, each end plate being provided with a perforated area which is concentric with the longitudinal axis of the body.

5. A muffler according to claim 1 in which the tubular shell portion and the tubular passage part of each body are interconnected by a moulded member of foamed synthetic resin bonded to the said tubular members.

6. A muffler according to claim 1 in which the locking means comprises stay bolts having nuts and adapted to be fitted to the bodies forming the gables of the muffler.

7. A muffler according to claim 1 inwhich the locking means comprises a tubular shroud portion slit in its longitudinal direction and provided with clasping members to force the edges of the slit portion together.

8. A muffler according to claim 7, in which the bodies are provided with motion transferring means insuch a manner that the turning of one body over a certain angle will bring about the turning of at least one adjacent body.

9. A mufiler according to claim 8 in which the motion transferring means comprises an elongated slot in one end plate of the body being concentric to the outer shell and of a pin at the appropriate portion of the adjacent body. 

